package com.proj.mausoleum.utils;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

public final class Captcha {
    private Captcha(){}

    // 随机字符字典
    private static final char[] CHARS = { '2', '3', '4', '5', '6', '7', '8', '9' };

    // 随机数
    private static Random random = new Random();

    // 获取6位随机数
    private static String getRandomString() {
        StringBuffer buffer = new StringBuffer();
        for(int i = 0; i < 4; i++) {
            buffer.append(CHARS[random.nextInt(CHARS.length)]);
        }
        return buffer.toString();
    }

    // 获取随机数颜色
    private static Color getRandomColor() {
        return new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255));
    }

    // 返回某颜色的反色
    private static Color getReverseColor(Color c) {
        return new Color(255 - c.getRed(), 255 - c.getGreen(),255 - c.getBlue());
    }

    public static void outputCaptcha(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("image/jpeg");
        // 获取验证码字符串
        String code = getRandomString();
        request.getSession().setAttribute("code", code);

        int width = 70;
        int height = 25;

        Color color = getRandomColor();
        Color reverse = getReverseColor(color);

        BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics2D g = bi.createGraphics();
        g.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 16));
        g.setColor(color);
        g.fillRect(0, 0, width, height);
        g.setColor(reverse);
        g.drawString(code, 18, 20);
        for (int i = 0, n = random.nextInt(100); i < n; i++) {
            g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);
        }
        // 转成JPEG格式
        ServletOutputStream out = response.getOutputStream();
        ImageIO.write(bi, "jpeg", out);
        out.flush();
    }
}
